Detailed Explanation of the Key Technical Points of Jujube Tree Cultivation and Management

The jujube tree is also known as jujube fruit, Chinese date, spiny jujube, and guanjujube. It is a plant of the genus Ziziphus in the buckthorn family (Rhamnaceae), a deciduous small tree, rarely a shrub, reaching more than 10 m in height, with brown or grayish-brown bark. It grows in mountainous areas below 1700 m in elevation, on hills or plains. It is widely cultivated. This species is native to China, and is often cultivated in Asia, Europe, and the Americas. Below is an introduction to the cultivation and management techniques for jujube trees.

I. Orchard Selection and Planting

The jujube tree is highly adaptable, but it grows and develops better under conditions of loose soil, deep soil layers, and sufficient fertilizer and water. Planting jujube trees in cultivated land in a planned way and implementing jujube-grain intercropping is an effective way to develop three-dimensional agriculture and achieve a double harvest of jujubes and grain. Both sides of canals and roads, field edges and ridges, and courtyards are all good places for developing jujube trees. It can also be combined with the establishment of farmland shelterbelts to build a multifunctional, high-benefit composite forest-fruit commercial production base.

Planting can be done in both spring and autumn, but spring is better. It is generally carried out within one week before the jujube trees bud. Planting density: for a contiguous jujube orchard, the spacing between plants and rows is 4-5 m × 5-6 m, with 22-33 trees per mu; for long-term jujube-grain intercropping, the row spacing is 8-15 m and the plant spacing is 4-6 m, with north-south rows used for planting. The size of the planting hole is generally 80 cm square, and more than 10 kg of farmyard manure is applied. The planting depth should be level with the root collar, backfilling while tamping down, straightening the seedling, and watering immediately after planting. When planting, dipping the seedling roots in phosphate fertilizer slurry helps survival.

II. Fertilizer and Water Management

To promote early fruiting and early high yield of jujube trees, soil, fertilizer, and water management must be strengthened. In the Hexi irrigation district, aside from winter irrigation, the number of irrigations is mostly the same as that for wheat; for fertilization, apply 0.15-0.25 kg of diammonium phosphate per tree, choose reasonable intercrops to facilitate ventilation and light penetration; leave sufficient tree to ensure nutritional area, and after planting, promptly determine the trunk height and pay attention to pruning.

1. After the soil thaws, carry out deep plowing within a 2 m radius around the jujube tree to improve soil aeration. Loosen the soil and remove weeds in time; spring plowing should be shallow, and autumn plowing should be deep;

2. Apply base fertilizer before freezing in late autumn, and apply topdressing before sprouting in spring. Generally, for a single tree producing 50 kg of fresh jujubes, apply 100 kg of coarse manure or a mixture of 1.5 kg each of nitrogen and phosphorus fertilizers and 0.5 kg of potassium fertilizer in furrows. When fertilizing, dig a ring-shaped trench of 40 × 40 cm at 1-1.5 m from the trunk and apply the fertilizer into it. During the flowering period and the young fruit growth period, apply 0.5-1 kg of urea per tree by the radial trench method;

3. In places with irrigation conditions, irrigate in time before the flowering period, during fruit set, during the fruit enlargement period, and just before winter.

III. Training and Pruning

After planting, the trunk height must be determined. Trunk height: about 1 m for contiguous jujube orchards, and about 1.5 m for jujube-grain intercropping. Pruning is generally carried out in winter and spring. In the first three years, light pruning should be the main approach, combining promotion and control, leaving more branches so that the canopy forms as quickly as possible. At the same time, actively cultivate high-yield tree shapes. The main ones are the central-leader delayed-open form, the multi-main-branch natural round-headed form, and the open-center form. When pruning fruit-bearing trees, control water sprouts, retain normal branches, and cut out diseased and dead branches. Mainly use heading back, remove diseased branches, dead branches, overlapping branches, and upright branches, control water sprouts, and renew aging branches. Summer pruning adopts methods such as pinching, thinning, removing suckers, and adjusting branch positions to regulate nutrient distribution and achieve ventilation and light penetration within the canopy.

Training and pruning is an important technical measure in jujube cultivation. In the past, without training and pruning, after determining the trunk height, no pruning was done except cutting off dead branches, allowing natural growth and natural renewal, which resulted in disordered branches, unclear layers, aging tree vigor, outward movement of fruiting positions, many flowers, few fruits set, low and unstable yield, and low economic benefits. With the development of jujube production, relevant research institutions, on the basis of strengthening soil, fertilizer, and water management for jujube trees, carried out training and pruning trials and preliminarily worked out a set of pruning methods to balance branch vigor, open the light path, and adjust the relationship between fruiting and growth, thereby achieving high yield, high quality, and a long fruiting life.

The jujube shoot (zaotou) is the basis for forming the jujube tree framework and fruiting base branches. It is mostly formed by sprouting of main buds and has vigorous extension ability. After growth stops, a terminal bud forms at the top, which sprouts the next year to continue extending growth, or it may sprout and grow twice in one year. Its thickening ability is very strong. The training of jujube trees mainly depends on jujube shoots, using them to expand the fruiting area, increase new jujube spurs, and provide conditions for increasing yield and renewal of jujube trees.

The secondary branch of the jujube shoot (fruiting base branch) generally has 5-10 nodes, and each node also has main and accessory buds. The main bud does not sprout in the same year, and forms a jujube spur the next year. Therefore, the secondary branch is the basis on which jujube spurs are borne, while the accessory bud sprouts in the same year to produce jujube pendants. Although such jujube pendants can generally bloom, they set few fruits, and the fruits are small with poor quality. Pinching is often used to increase the fruit-setting rate and promote fruit development.

The main buds borne laterally at the base of the secondary branch of the jujube shoot generally do not sprout in the same year, remaining dormant, or form jujube spurs the following year and continue to produce jujube pendants that bear fruit. However, under certain conditions, such as stimulation (mechanical damage or sufficient water and fertilizer), such jujube spurs can also sprout jujube shoots. But under conditions of weak tree vigor or poor nutrition, jujube shoots can also transform into jujube spurs. This mutual transformation of branches and buds is the main basis for jujube pruning.

The jujube spur is a shortened fruiting mother branch. The vast majority are formed by sprouting of main buds on secondary branches, and the jujube spurs in the middle part of secondary branches are of better quality. The terminal bud of the jujube spur is a main bud, which continues to grow every year, but the growth amount is very small, only 1-2 mm. As the terminal bud of the jujube spur grows, the accessory buds around it produce 2-5 jujube pendants, and later, as the age of the jujube spur increases, the number of jujube pendants also increases. Under normal circumstances, the terminal bud of the jujube spur sprouts only once a year. When it sprouts and produces jujube pendants, the top simultaneously forms a terminal bud and stops growing. If nutrition is sufficient and it is stimulated by disaster or heading back, it will produce jujube pendants a second time, bloom and bear fruit, while itself elongating another 1-2 mm. These characteristics are manifestations of the functional specialization of different branch types in jujube trees, and are also favorable traits for high and stable yield of jujube trees.

As for the fruiting ability of jujube spurs, generally the jujube spurs borne on fruiting base branches (secondary branches) and those growing upward have strong fruiting ability. Jujube spurs aged 3-7 years have the strongest fruiting ability; young (1-2 years) and old (over 10 years) jujube spurs have poorer fruiting ability. The lifespan of jujube spurs is generally 6-15 years, but it is also closely related to their bearing position, cultivated variety, and environmental conditions. Jujube spurs on the primary branch of the jujube shoot have a longer lifespan, while those on fruiting base branches (secondary branches) have a shorter lifespan, but the number of jujube spurs borne on fruiting base branches is large (accounting for 80-90%), fruiting is stable, and branching ability is strong. Therefore, on the basis of comprehensive management, correctly applying pruning techniques to cultivate a large number of robust jujube spurs with strong fruiting ability is an important way to obtain high yield in jujube trees.

The jujube pendant is the fruiting branch of the jujube, and because it is soft and drooping it is also called a “jujube pendant&rdquo. Jujube trees rely entirely on jujube pendants for fruiting. Jujube pendants fall off with the leaves in autumn, so they are also called deciduous fruiting branches, or simply deciduous branches, which is one of the characteristics of jujube branches.

Each leaf axil of a jujube pendant can bear 3-15 flowers, and the flowers on the middle and upper nodes set fruit better. Generally, jujube pendants do not have branching ability, but if a jujube pendant falls off during the growing season for some reason, new jujube pendants can still sprout from the original jujube spur, giving it the characteristics of multiple sproutings and multiple fruiting.

The flower bud differentiation of jujube differs from that of other fruit branches. Before winter, the flower primordium does not appear in the bud; flower buds differentiate in the leaf axils when the jujube pendant begins to sprout. Therefore, increasing the nutrition of jujube spurs before winter is beneficial to flower bud differentiation. In addition, the flower bud differentiation of jujube trees is characterized by sprouting in the same year, differentiating in the same year, multiple differentiation, a short differentiation period, fast differentiation speed, and long duration. To increase yield and adapt to the characteristics of flower bud differentiation, attention should be paid to strengthening soil, fertilizer, and water management in the early stage, so as to preserve leaves, improve nutrition, promote differentiation, and increase the fruit-setting rate, thereby increasing yield.

IV. Pruning Periods

Pruning periods are generally divided into winter pruning and summer pruning. Winter pruning can generally be carried out from after leaf fall until before sap flow in the following year, but because jujube trees have a long dormancy period, poor healing ability, and spring winds are strong, winter pruning is not easy to carry out, so March-April is generally suitable. In other words, spring pruning is better, but by convention it is still called winter pruning. Summer pruning is carried out from late June to early July, after the vigorous growth stage of jujube shoots has passed and begins to slow down.

V. Pruning Methods

There are five commonly used methods: thinning, renewal pruning, heading back, pinching, and scoring.

1. Thinning: a pruning method of removing from the base the dried branches within the canopy, unusable water sprouts, drooping branches, and overly dense branches. Thinning can concentrate nutrients in the tree, achieve appropriate density, provide ventilation and light penetration, and balance branch vigor.

2. Renewal pruning: the shortening and pruning of perennial extension branches and fruiting branches. It can raise the angle of the branch tip, increase growth vigor, and help rejuvenate branch groups and renew old trees.

3. Heading back: cutting a relatively long branch shorter. Its function is to increase nutrients in the lower part, stimulate the sprouting of main buds, promote the production of new branches, and ensure robust tree vigor and normal fruiting.

4. Pinching: removing the terminal bud of a new jujube shoot during the growing season to reduce the elongation growth of the jujube shoot and increase the fruit-setting rate.

5. Scoring: making a cut 1 cm above the main bud to promote the sprouting of new branches. It is generally not commonly used; for convenience, heading back is mainly used.